Laminated transparent polarizing glasses and method of making

ABSTRACT

This invention is directed to the production of laminated, transparent, polarizing glass articles. The inventive method contemplates five basic steps: 
     (1) forming parallel microgrooves on a surface of a glass support; 
     (2) washing and drying said surface; 
     (3) depositing on said surface a mixture of organic colorants corresponding to the three primary colors and exhibiting a nematic state to yield a coating displaying polarizing properties; 
     (4) treating the polarizing coating with an aqueous solution of inorganic salts having an acid pH; and 
     (5) applying a continuous, optically transparent, composite film upon the polarizing coating and bonding it thereto.

This is a division of application Ser. No. 06/734,848, now abandoned,filed May 16, 1985, which is a continuation of application Ser. No.446,551, filed Dec. 3, 1982, now U.S. Pat. No. 4,865,668.

BACKGROUND OF THE INVENTION

Transparent, laminated, light polarizing glasses are used extensively inthe making of medical, ophthalmic, sun, and protective spectacle lenses,but they could also be utilized in other fields as, for example,instrument lenses, windows for vehicles of all kinds (air, sea, land),windows for buildings, and the like.

The manufacture of polarizing glasses raises various problems related tothe solubility of the polarizing materials (generally the polarizingparticles) in the surrounding environments (water, chemical productseven in weak concentrations, etc.), as well as their very low mechanicalstrength. This has led researchers to devise various means of protectionas, for example, by incorporating the polarizing particles in a polymerfilm.

In general, the products are recognized as having very low surfacehardness, a very marked sensitivity to scratching, and anincompatibility with the majority of the current cosmetic products.

For all that, attempts to obtain glass lenses have consisted inassociating an organic polarizing film of the polyvinyl alcohol typewith one or two ("sandwich") elements of glass. These attempts have comeup against a number of difficulties such as:

the complexity of bonding the polarizing film to an optical substratewithout deforming the direction of polarization, as indicated in FrenchPatent No. 76.18891, filed Jun. 22, 1976 by American OpticalCorporation;

the weight of the assemblies thus obtained are not compatible with, forexample, the conventional lenses utilized in spectacles (10-25 grams);and

the extremely high cost of such products which is a result of theircomplexity.

For these reasons, these products are not much used for applications ofthe "general public" type such as spectacle making.

More recently, attempts were conducted to provide polarizing films ofthe polyvinyl acetate or polyvinyl butyrate type bonded onto the concaveface of an inorganic spectacle glass. This approach also provedfruitless because of three major difficulties:

the very poor optical quality of such films;

the necessity for protecting them from moisture; and

their sensitivity to scratching.

In spite of all these handicaps, a product of this type is available incommerce under the name of "POLAROID" lenses. In this product thepolarizing material is contained in polyvinyl films laminated front andback to thin films of cellulose and protected by a thin strip ofmelamine.

As with all materials of this type, the great disadvantage in using thistype of product is its very great sensitivity to scratching whencompared to conventional products which are inorganic glasses.

In addition to all this, all the products currently (or formerly) on themarket do not satisfy a present need of consumers which is to have attheir disposal inorganic photochromic glasses (that is to say an opticaltransmission which varies with the conditions of lighting) andpolarizing, colorable, and/or filtering if it is needed. Such a productin order to be perfectly suitable, should not be subject to anylimitation about the design of the shape and the radius of curvature inorder to satisfy, without any restriction, all the needs for makingmedical, ophthalmic, and protective spectacles.

SUMMARY OF THE INVENTION

The present invention aims to provide a laminated, transparent,polarizing glass which is free of the deficiencies reviewed above andpermits satisfaction of the above-mentioned needs.

More precisely, the invention is concerned with a laminated,transparent, polarizing glass characterized in that it comprises:

(a) a support of inorganic or organic glass;

(b) a coating with polarizing properties deposited upon one of the facesof the support; and

(c) an optically transparent, continuous composite film constituted onone side by a thickness of thermoplastic polyurethane with adhesiveproperties, and on the other side by a thickness of thermosettingpolyurethane with anti-lacerating and self-healing properties, thethermoplastic polyurethane side adhering to the coating with polarizingproperties.

The invention is also concerned with a process for obtaining such alaminated, transparent, polarizing glass characterized in that itcomprises the following steps:

(a) forming parallel microgrooves on a surface of an inorganic ororganic glass support which is to receive the polarizing coating, thesegrooves frequently being made with the aid of a very gentle abrasion ofthe aforesaid support;

(b) carefully washing the surface of the support which is to receive thepolarizing coating and drying this surface;

(c) depositing on the washed and dried surface of the support a mixtureof three organic colorants corresponding to the three primary colors andexhibiting a nematic state to form a coating demonstrating polarizingproperties;

(d) treating the resulting polarizing coating with an aqueous solutionof inorganic salts having an acid pH (normally by immersing into saidsolution) in order to reduce the water solubility of the aforesaidpolarizing coating; and

(e) applying the composite film of polyurethane by subjecting it firstto moderate temperature and pressure conditions in order to insure awrinkle-free and gradual flow or spreading out and an adherence of thefilm upon the polarizing coating, and thereafter to elevated temperatureand pressure conditions to reinforce the mechanical bond between thefilm and the coating and to complete the crosslinking of the compositefilm.

As is illustrated in FIG. 1, the support 1 can be composed of aninorganic or organic glass of any composition and shape. This can be,among others, a glass exhibiting photochromic properties; in particular,a blank of spectacle glass (corrective, solar, or protective).

The polarizing coating can be of various types. One type of suitablepolarizing coating is formed of a mixture of three colorantscorresponding to the three primary colors blue-red-yellow and exhibitinga nematic state. The colorant molecules are oriented spontaneously onthe base support through the grace of a pre-alignment created by a veryslight abrasive parallel brushing of the surface of the support to becoated. This brushing creates parallel microgrooves of very little depthand width (less than 0.5 μm). The coating obtained exhibits a dichroiceffect in the vicinity of 10 and a high water solubility. One can reducethis water solubility by a surface stabilization treatment with the aidof an aqueous solution of inorganic salts having an acid pH. Suitableorganic colorants are sold by, among others, the 3M Company of St. Paul,Minn., U.S.A., under the brand name "3M Veri-light 25".

Techniques concerning this type of polarizing coating can also be foundin U.S. Pat. Nos. 2,544,659 and 2,481,830.

The composite film (3) is advantageously composed of the composite filmdescribed in British Patent No. 1,576,394.

According to a preferred embodiment, a continuous composite film isconstituted on one side by a thickness of thermoplastic polyurethane,and on the other side by a thickness of thermosetting polyurethane, theaforesaid thermoplastic polyurethane being joined to the coatingexhibiting polarizing properties and being formed from an aliphaticdiisocyanate and an aliphatic diacid polyester diol or a polyglycolether diol, each of said diols having a molecular weight of 500-4000,and said thermosetting polyurethane being the product of (a) apolyglycol ether resulting from the combination of epoxy-1,2 propanewith 2,2-bis(hydroxymethyl)1-butanol and containing 10.5-12% by weightof free hydroxyls, and (b) a biuret of 1,6-hexamethylene diisocyanatecontaining 21-22% by weight of isocyanate groups, the weight of saidbiuret being composed of between 0.9 and 1.1 times the weight of saidpolyglycol ether, the thickness of the thermoplastic polyurethaneranging about 0.01-0.8 mm and the thickness of the thermosettingpolyurethane ranging about 0.2-0.8 mm.

The application of this composite film (3) upon the polarizing coating(2) is effected through the application of heat and pressure, as will bedescribed in more detail below.

Once the laminated transparent glass with three plies 1-2-3 iscompleted, it can be subjected to any possibly necessary finishingoperations. For example, in the case where the laminated glass is ablank for a spectacle lens, it can be subjected to the operation called"edging" (finishing of the contour in order to fit the glass to theshape of the frame into which it is to be affixed).

This edging operation has the disadvantage of breaking the thin skinlayer formed upon the polarizing coating at the level of the edge of theglass so that there exists a risk that moisture may penetrate into thelaminate and eventually bring about a destruction of the polarizinglayer through unsticking, as tests of resistance to atmospheric agentshave shown. In order to surmount this difficulty it is advisable,according to the invention, to protect the edge of the glass, afteredging the latter, with a coating of a resin which is polymerized insitu.

The inventive laminated glasses exhibit polarizing effects rangingbetween 50-98% and optical transmissions at 2 mm ranging between 25-45%,those values being a function of the quantities of polarizing molecules,their structure, and their dichroic effect. These products conformperfectly to all the prevailing standards in the field of spectaclemaking.

It is fitting to note, in passing, that the inventive laminated glassescan then be colored, if desired, by the process described in FrenchPatent Applications No. 81.22718 filed by the Applicants on Dec. 4,1981. In this manner, it is possible to easily produce new and desirableproducts, namely, photochromic polarizing glasses which are easilytintable and which are able to cut off ultraviolet radiation and havethe widest variety of shapes and curvatures without any limitation.

Finally, although in the present application reference is made morespecially to a laminated glass destined for spectacle making, thisapplication is not so limited. As a matter of fact, such glass can findperfect application in other fields, for example, as windows forvehicles (automobiles, boats, trucks) or for buildings, or as readingwindows of digital indicators utilized in electronic instrumentation ortimepieces under the name "liquid crystal display". Generally speaking,the invention is useful in all fields where polarization of incident orreflected light can provide comfort or increased technical possibilitiesto the user.

The description which follows, presented with respect to the attacheddrawings, given by way of non-limiting examples, will make it easy tounderstand how the invention can be carried out, the particularitieswhich appear both in the drawings and in the text do, of course, formpart of the said invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in cross section of a laminated polarizing glassaccording to the invention; and

FIG. 2 is a schematic view illustrating the protection of the edge of aspectacle glass lens according to the invention through a coating ofpolymerized resin.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 is shown a laminated polarizing glass according to theinvention; more precisely, a blank for a spectacle glass machinedaccording to the requisite optical specifications. The glass iscomprised of a support 1 of an inorganic or organic glass with orwithout photochromic properties, a polarizing coating 2 deposited uponthe concave face of the support, and an optically transparent,continuous composite film 3 composed of a layer 4 of thermoplasticpolyurethane having adhesive properties and a layer 5 of thermosettingpolyurethane having anti-lacerating and self-healing properties, thethermoplastic polyurethane adhering to coating 2.

In FIG. 2 is shown a spectacle glass lens made into the desired shapethrough edging the blank of FIG. 1. The glass is provided on its edgewith a coating 6 of resin polymerized in situ for protection against thepenetration of water.

A glass support endowed with photochromic properties constitutes apreferred embodiment of carrying out the invention.

The following is a non-limiting example illustrating the invention.

EXAMPLE

The application of the polarizing coating upon an inorganic photochromicglass support is effected as follows in eight phases:

Phase 1: Preparation of the Surface

This step has the objective of permitting a pre-alignment of the organicmolecules to be deposited through a very slight abrasive brushing of thesurface to be covered. To this end one can utilize, for example, a thickrotary disc, preferably polyester foam impregnated with an abrasive,such as an oxide of the zirconia type (ZrO₂) or, preferably, alumina(Al₂ O₃) in suspension in water. The edge of the disc is applied againstthe surface so as to form parallel microgrooves in the latter. Theduration of the operation can take, by way of illustration, about 3-30seconds, the time being a function of the surface hardness of thesupport to be covered. Ordinarily, 10 seconds will be sufficient forinorganic glasses.

Phase 2: First Washing of the Surface

This operation has the objective of clearing the surface of theinorganic oxide residues utilized in the preceding step. This can beeffected, for example, by brushing the surface with apparatus similar tothe preceding step but wherein the abrasive in suspension is replacedwith natural water at ambient temperature. This operation lasts, forexample, about 10-30 seconds.

Phase 3: Second Washing of the Surface

This operation has the objective of chemically preparing the surface tobe covered to give it a high level of cleanliness. In this operation thesupport, preferably subjected to a movement of horizontal rotation (forexample at 500 rpm), is continuously sprayed with deionized water havinga resistivity of about 10-17 ohm cm which, depending upon the support,may or may not contain a small proportion of a surface tension agent(for example 1% by volume alcohol). The duration of this operation is,for example, on the order of 5-10 seconds.

Phase 4: Drying of the Surface

One dries the surface of the support, previously prepared by a veryclean rinse, for example by exposure of the support, while rotating,under a 75-watt I.R. lamp for several seconds (for example 5-10seconds).

Phase 5: Stabilization of the Support

In this operation the support to be covered is stabilized to temperatureand humidity for about 1 minute and 30 seconds in a cabinet at 30° C.±1°C. and 50%±5% humidity. The same cabinet is utilized for the followingphase.

Phase 6: Deposition of the Polarizing Coating

In this phase organic molecules of the "nematic" type, comprised of amixture of three azo-based colorants (blue-red-yellow) in solution inwater, are deposited and oriented. The proportion of the three colorants(marketed by the 3M Company under the name "3M Vari-Light 25") isdetermined so as to obtain a maximum polarizing effect, which effect islinked to the formation of elongated crystals in very precise ranges oftemperatures and humidities (30°±1° C. and 50±5% relative humidity). Theresulting coating has a slight gray color. A slightly alkaline wettingagent is generally associated with the mixture of colorants, its rolebeing to promote the formation of aggregates of organic molecules. Theconcentrations of the recommended wetting agent are on the order of afew percent, preferably 1-2% by volume.

In this phase the support is sprinkled with the solution of organicmolecules in the ratio of about 1.5-5 ml of liquid for a support havinga diameter between 50-80 mm. The support is set in a horizontalrotation, for example, 1000 rpm, during, for example, 30-45 seconds, inorder to orient the organic molecules according to the pre-alignmentgenerated previously through brushing, and to evaporate throughcentrifugation the solvent of the initial solution. The deposit obtainedexhibits a dichroic effect in the vicinity of 10 and a high solubilityin water. The quantity of the solution of organic molecules and thespeed of centrifugation impart to the support a level of polarizationranging between about 90% and 50% for optical transmissions at 550 nmranging between 25% and 45%.

Phase 7: Stabilization Treatment of the Surface

This step has the objective to reduce the water solubility of thepreviously formed, polarizing coating. To accomplish this the supportsare treated by immersion for 10 seconds into an aqueous solution ofinorganic salts having an acid pH (for example 3.2). The inorganic saltsgenerally employed are mixtures of iron and calcium salts in aqueoussolution. This produces an ionic diffusion in the surface with theformation, with the organic colorant molecules, of a metal sulfonatewhich is insoluble in water. Other salts which are usable are describedin above-cited U.S. patents.

Phase 8: Last Rinsing of the Surface

In this step the product obtained is rinsed through total immersion intonatural water at ambient temperature.

The lens produced is polarizing and the treatment of the surfaceoperates to impart an effective insensitivity to water to the surface ofthe polarizing coating.

The application of the composite polyurethane film can be effected asdescribed in the British patent previously cited, but it is preferablyproduced as described in French patent application No. 81.18678, filedOct. 5, 1981 by the Applicant under the title "Laminated OphthalmicGlass and Method of Making", except that the operation of cleaning theglass lens is omitted. Briefly, this process consists in placing thethermoplastic polyurethane side of the composite film into contact withthe polarizing coating carried by the support, pressing the compositefilm against said coating at ambient temperature or at a moderatelyelevated temperature (40°-80° C. for example) and under a moderatelyelevated pressure (3-5 bars for example), in order to insure a uniformlyprogressive flow or spreading free from wrinkles and an adherence of thefilm upon the coating, and then subjecting the resulting laminate toelevated temperatures and pressures (75°-150° C. and 5-25 bars, forexample) for a sufficient length of time (0.5-4 hours, for example) inorder to reinforce the mechanical bond between the composite film andthe polarizing coating, and to eliminate gaseous inclusions.

The resulting laminated glass lens blank can be subjected, if necessary,to edging. This edging is carried out on a blank previously heated to110° C.±10° C. for about 30 minutes in order to temporarily increase theadherence of the polarizing coating to the composite film.

After edging, a thin layer of organic resin capable of being polymerizedin situ is applied to the edge of the glass lens in order to physicallyprotect the polarizing coating against possible penetration of water. Itis possible to use, for example, a resin polymerizable by ultravioletradiation such as the resin LOCTITE® marketed in France by the SocietyFRAMET in Senlis. A treatment of 5 seconds with a 1500-watt xenonultraviolet lamp suffices to harden this resin.

The protective coating of resin is polymerized to a thickness of a fewhundredths of a millimeter and is perfectly transparent and colorless.The finished glass obtained can then be mounted in spectacles withoutany fear of deterioration, as demonstrated by tests of more than 252hours at 50° C. and 98% relative humidity in a weathering chamberfollowed by an extended immersion in water (several weeks).

We claim:
 1. A laminated, transparent, polarizing glass articleexhibiting a level of polarization ranging between about 90% and 50% foroptical transmissions at 550 nm ranging between 25% and 45% consistingessentially of:(a) a support of inorganic glass having parallelmicrogrooves in one face thereof; (b) a coating exhibiting polarizingproperties on said face of said support, said polarizing coatingcomprising a mixture of three organic colorants corresponding to thethree primary colors and exhibiting a nematic state, the organicmolecules of which are oriented to align with said parallelmicrogrooves; (c) the surface of said face having a metal sulfonatediffused therein; and (d) a continuous, optically transparent compositefilm consisting of a layer of thermoplastic polyurethane having adhesiveproperties and a layer of thermosetting polyurethane havinganti-lacerating and self-healing properties, said thermoplasticpolyurethane layer being adhered to said coating exhibiting polarizingproperties.
 2. A glass article according to claim 1 wherein said supportis an inorganic glass displaying photochromic properties.
 3. A glassarticle according to claim 1 which is destined for use as a blank for aspectacle lens which blank is subjected to an edging operation, whereinthe edge of said blank has a coating of resin thereon which ispolymerized in situ.
 4. A glass article according to claim 1 whereinsaid thermoplastic polyurethane layer is formed from an aliphaticdiisocyanate and an aliphatic diacid polyester diol or a polyglycolether diol, each of said diols having a molecular weight of 500-4000 andsaid thermosetting polyurethane is the product (a) of a polyglycol etherresulting from the combination of epoxy-1,2 propane with2,2-bis(hydroxymethyl) 1-butanol and containing 10.5-12% by weight offree hydroxyls, and (b) a biuret 1,6-hexamethylene diisocyanatecontaining 21-22% by weight of isocyanate groups, the weight of saidbiuret being composed of between 0.9-1.1 times the weight of saidpolyglycol ether, the thickness of the thermoplastic polyurethane layersranging about 0.01-0.8 mm and the thickness of the thermosettingpolyurethane layer ranging about 0.2-0.8 mm.